Coelacanth fishes from the continental Triassic of the western United States. American Museum novitates ; no. 2036

Abstract:

"There is now conclusive evidence that coelacanths are present in both the lower and the upper Triassic continental beds of the western United States. The scarcity of their remains is, in part, related to the factors that are responsible for the general rarity of fishes in these formations. The broad, flat, flood-plain environment in which the Moenkopi and Chinle-Dockum sediments were deposited (McKee, 1954; Stewart et al., 1959) was apparently more favorable for the preservation of terrestrial than of aquatic vertebrates. Metoposaur and phytosaur remains are much more abundant and more widely distributed than fish remains. The latter are restricted, as might be expected, to channel and lacustrine deposits. Although isolated actinopterygian scales are reasonably common in such deposits, associated fish remains are extremely rare. At a few localities in the Chinle complete fishes have been found in great abundance. These usually occur in lacustrine deposits in concentrations suggestive of periodic mass mortality. The apparent rarity of coelacanth remains in these concentrations suggests that they were not common in the lakes and ponds of the Chinle flood plain. On the other hand, there is no positive evidence that they were, in general, restricted to rivers and streams. Except for the Moenkopi occurrence, which is quite clearly fluviatile, the paleoecologic picture is unsettled. Isolated coelacanth bones from the Moenkopi formation include distinctive basisphenoids, the morphology of which provides the basis for establishing a new genus and species, Moenkopia wellesi. Specimens thus far recovered from the late Triassic Dockum and Chinle formations are too incomplete to permit generic identification"--P. 15-17.

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American Museum NovitatesNovitates (Latin for "new acquaintances"), published continuously and numbered consecutively since 1921, are short papers that contain descriptions of new forms and reports in zoology, paleontology, and geology. New numbers are published at irregular intervals.